Metering pump



Jan. 9, 1968 E. L. ECKFELDT ET AL 3,362,339

METERING PUMP 2 Sheets-Sheet 1 Filed Oct. 1, 1965 Jan. 9, 1968 1.. ECKF'ELDT ET AL 3,362,339

. METERING PUMP Filed on. 1, 1965 2 Sheets-Sheet 2 United States Patent 3,362,339 METERING PUMP Edgar L. Eckfeldt, Ambler, and Earl W. Shaffer, Jr., Elhins Park, Pa., assignors to Leeds & Northrup Company, a corporation of Pennsylvania Filed Oct. 1, 1965, Ser. No. 492,114 24 Claims. (Cl. 103-132) This invention relates to positive displacement rotary pumps and especially those of low and exact flow rates in the zero to milliliter range which have minimum external and internal leakage and maximum chemical resistivity.

Numerous examples in various areas of technology can be cited where it is necessary to regulate the flow of a fluid with precision, such as in chemical processes where the flow of one solution into another must frequently be regulated to achieve proper proportions of the two solutions on mixing. Exact flow control is often a prerequisite of a measurement system. Examples of analytical methods that require precise control of liquid flow include the following techniques: electrophoresis, liquid chromatography, continuous colorimetry, continuous calorimetry, automatic titration and derivative coulometry. In these techniques the flow rate must not only be held constant over periods of time but also the solution flow must be free of pulses and other short term changes in flow rate.

In addition to flow rate characteristics, there are a number of other factors that are important in many solution metering applications. A high degree of chemical resistivity is usually needed in the materials used in construction of the pump, because chemically active solutions must be handled by the pump. If the materials of construction are attacked by the pumped solution, the component parts of the pump will corrode and deteriorate, leading to poor service life. Furthermore, contamination or change in the solution being pumped arising from corrosive action often cannot be tolerated. For this reason lubricating substances that can leak into the sample stream are objectionable. Further, rapid solution transit through the pump (small holdup volume inside the pump), is desirable.

Commercially avail-able pumps will not meet the exacting requirements set out above in that in the first instance, their flow rates are unstable due to internal leakage as well as external leakage. Further yet, metering pumps presently available do not have the necessary chemical resistivity or anti-contamination characteristics required in that these pumps, in one way or another, will have some corrosive element susceptible to attack by the fluid being pumped.

Accordingly, it is an object of the present invention to provide a positive displacement rotary pump having low internal and external leakage and a consequent exact and continuous flow rate of the type utilizing an impeller race member having a pumping chamber in the member and an impeller disposed within the race member and supported for orbital pumping action therein in combination with side wall members disposed on the adjacent sides of the race member, at least one of which is a flexible side wall whereby the flexibility of the flexible side wall will adjust for normal wear and dimensional discrepancies between the impeller race member and the impeller thus maintaining a continuous fluid-tight seal.

It is a further object of the present invention to provide a rotary pump having a precise flow rate as a result of low internal leakage of the type employing an impeller member supported for orbital pumping action within a pump body member and an impeller vane disposed be tween the pump body member and the impeller member where the impeller vane is secured to one of the members and is movable in an impeller vane guide in the other wherein the impeller vane guide has two oppositely disposed side walls formed integral with one of the members,

at least one of which is a flexible and resilient side wall spaced from the other a distance less than the thickness of the impeller vane in order that, during pumping action of the impeller, the flexible and resilient action of the side wall of the vane guide will provide a fluid-tight seal between the vane guide and the impeller vane.

It is still another object of the present invention to provide a rotary pump with high chemical resistivity having no internal contamination as well as a pump having low internal and external leakage by the utilization of chemically inert materials, especially fluorocarbon plastic materials in association with all of the components of the pump which are or may come into contact with the chemical solution being pumped.

Other objects and advantages of the present invention will become apparent from the description thereof taken in conjunction with the drawings in which:

FIG. 1 is an isometric view of the pump of the present invention shown in relationship to its associated mounting means and driving means;

FIG. 2 is an exploded isometric view of the rotary pump of the present invention;

FIG. 3 is a sectional view of the rotary pump of the present invention taken along the lines 3--3 of FIG. 1; and

FIG. 4 is a detailed view of the impeller vane guide and associated vane guide biasing spring forming a part of the present invention.

Referring now to FIG. 1, the rotary pump 10 of the present invention is shown in assembled form and secured through stay bolts 11 to a mounting plate 12 which in turn is secured to a base member 13. A motor 14 which may be of a constant speed or a variable speed as desired is accordingly secured to the mounting plate 12 and drives the pump 10.

The general relationship of the various components of the rotary pump 10 of FIG. 1 are best shown in the exploded isometric view of FIG. 2 and the Sectional view of FIG. 3. This relationship will now be described in a general manner in view of these two figures. First, it will be noted that the pump of the present invention includes components symmetrically disposed on either side of a central side wall 15. Disposed On either side of this central side wall 15 is an impeller race ring 16 which has a circular pumping chamber 17 therein in which is disposed a circular impeller 18. Disposed concentric within the impeller 18 in a suitable journal therefor is an eccentric cam 19 having a pump shaft hole 20 therein including driving pin slots 41. The pump shaft hole 20 is offset from the center of the eccentric cam 19 and thus provides the eccentric or orbital motion responsible for the pumping action of pumps of this general type. An impeller vane 26 is disposed between the impeller 18 and impeller race ring 16 and has one end thereof secured to the impeller and the other end in an impeller vane guide to be later described in detail in conjunction with FIG. 4-.

A flexible side wall 27 is disposed adjacent each impeller race ring 16 and associated impeller 18 and thus, when in assembled form, the flexible side wall 27, impeller race ring 16, and the central side wall 15 define a pumping cavity in which the impeller 18 and its associated eccentric cam 19 operate. Each flexible side wall 27 is maintained in engagement with its respective impeller race ring 16 and impeller 18 therein by means of a pressure ring 28 having on the face thereof a resilient cushion 29. The pressure ring is backed up by three helical springs 30 positioned within an end bell 31 and held in compression by three spring seating screws 32 which are threaded into the end bell as best shown in FIG. 3.

When in assembled position, the various components of the pump are held in relative position one to another by the four stay bolts 11 (FIG. 3) and the pressure ring 28 is held in alignment with the end bell 31 by means of an alignment pin 33 in engagement with an alignment hole 34.

A suitable resilient element 35 is disposed between the end bell 31 and flexible side wall 27 to assure the maintenance of the proper sealing pressure between the various elements in the stacked array.

The eccentric cams 19 and associated impellers 18 are driven in their respective pumping chambers by means of an input shaft 36 which passes through the center of the pump and is journaled in end bearings 39. The input shaft 36 includes a central shaft encased in an outer sleeve 37 of a chemically inert material and the driving connection between the driving shaft and the eccentric cams is by means of eccentric cam pins 38 secured within the input shaft 36, which cam pins engage the pin slots 41 in the sides of the eccentric cams 19.

Having now generally described the relationship of the various components of the rotary pump of the present invention, attention will now be given to the specific details thereof.

The central side wall 15, impel-ler race rings 16, impellers 18, flexible side walls 27, impeller vanes 26, encasing 37 on the shaft 40, pins 38, and the eccentric cam 19 are all constructed of fluorocarbon plastic materials, preferably Tefion, with the exception of the eccentric cam 19, pins 38, and the casing 37 which are preferably of Kel-F. Teflon and Kel-F are trade names for the compounds polytetrafluoroethylene and polytrifluorochloroethylene respectively.

Accordingly, it will be appreciated from an examination of FIG. 3 that the fluid being pumped will never be in contact with any material other than the aforedescribed fluorocarbon plastic materials. Both Kel-F and Teflon are highly inert materials showing zero Water absorption characteristics and non-reactivity with almost every conceivable chemical material. Hence, the metering pump of the present invention is able to pump widely diverse chemical materials, including ones that have heretofore been considered unmanageable in conventional pump constructions, such as but not limited to, concentrated hydrochloric acid, hydrofluoric acid, and concentrated nitric acid. Further, the chemical inertness of the pump of the present invention has the added advantage of not introducing contamination to the fluid being pumped through corrosive attack of the fluid on the pump components.

Additionally, Teflon and Kel-F demonstrate a remarkable resistance to extremely low temperatures and extremely high temperatures in the range of 400 F. to 500 F. and accordingly, the pump of the present invention is capable of utilization with fluids in these extreme ranges.

Another feature of Kel-F and Teflon is the low coefficient of friction demonstrated by Teflon on Teflon and the superior bearing combination of Kel-F against Teflon. Thus, as all of the parts of the pump of the present invention which have relative movement one to another are of either Kel-F or Teflon material, the components therein will have exceedingly long life and low internal resistance without the need of additional lubrication.

Another feature of the rotary pump of the present invention, as best shown in FIG. 4, is the manner in which a seal is effected between the impeller vane 26 and the impeller race ring 16. This is accomplished by means of an impeller vane guide 45 formed integral with the impeller race ring 16. Relieved sections 46 adjacent each side of the impeller vane guide 45 provide reduced cross sections 47 on either side thereof. These reduced cross sections in combination with the flexible and resilient properties of Teflon allow the impeller vane guide 45 to be extremely resilient and flexible.

The width of the impeller vane guide 45 is preferably of lesser width than that of the impeller vane 26. Thus, the impeller vane guide 45 will provide an excellent fluidtight seal with respect to the impeller vane 26 as the latter is moving transversely within the impeller vane guide 45 in response to the orbiting action of the impeller 18 within the pump chamber 17 during operation of the pump.

If the fluid-tight seal between the impeller vane guide 45 and the impeller 26 is desired to be enhanced, a vane guide biasing spring 48 may be inserted within a substantially dumbbell shaped cavity 49 formed integral Within the impeller race ring 16 as shown in FIG. 4. The vane guide biasing spring 48 has inwardly curved portions 50 thereon which will urge the sides of the impeller vane guide 45 inwardly toward one another in accordance with the degree of preset spring tension built into the vane guide biasing spring.

One advantage of the impeller vane guide is that the vane guide biasing spring 48 is completely enclosed within the dumbbell shaped cavity 49 and is thus not subject to contact with the fluid being pumped. This arrangement protects the biasing spring from corrosion which in turn prevents contamination of the fluid being pumped.

However, as an additional precaution against corrosion and contamination of the fluid being pumped, the vane guide biasing spring 48 may be made of non-corrosive material or encased in a chemically inert material 54, preferably of fluorocarbon plastic material.

T 0 further insure proper sealing between the impeller vane 26 and the impeller vane guide 45, the impeller vane may have counter bores 51 therein which Will reduce the cross section thereof at the area closest the impeller 18. This reduced cross section will allow the impeller vane to deflect in the area of impeller 18 as the impeller is orbiting within the pumping chamber 17 and, in this manner, a straight translational movement of the impeller vane within the impeller vane guide 45 will be insured.

Another advantage of placing the vane guide biasing spring 48 completely within the impeller race ring 16 is that there is relatively little dead space existing in the area of the pump intake and discharge ports 52. Such an absence of dead space permits the retention inside the pump of only a very small amount of the fluid being metered. This results in rapid transit of a given portion of the fluid through the pump and accordingly, there is a minimum of time delay involved in transmitting the effect of a change in solution concentration being metered through the pump.

Although not shown in the drawings, it will be appreciated that the impeller vane guide 45 and associated cavity 49 and vane guide biasing spring 48 could as well be located in the impeller 18 and the impeller vane 26 secured to the impeller race ring 16. Additionally, the impeller vane 26 may be secured to the impeller 18 or impeller race ring 16 as the case may be by means of a fluorocarbon plastic pin 53 passing between and through the impeller vane and the member to which it is secured. This pin which is preferably of Kel-F will be a further protection against corrosion and contamination of the fluid being pumped.

In accordance with another aspect of the present invention, the flexible side wall 27, as best shown in FIG. 3, is held in engagement with the impeller race ring 16, impeller 18 and eccentric cam 19 by means of the pressure ring 28 previously described. The force exerted on the flexible side wall by the pressure ring is nearly constant throughout the flexible side wall as a result of the three helical springs 30 in engagement therewith and also due to the resilient cushion 29 on the face of the pressure ring 28, which ring insures an equal distribution of pressure and loading against the flexible side wall member.

The amount of compression of the resilient cushion 29 is not a factor in the loading force because the characteristics of the helical springs 30 under compression are designed to yield an approximately constant compression force despite small changes in the compression lengths.

The force exerted on the flexible side wall by the pressure ring 28 will insure that the impeller 18 and impeller race ring 16 will be in fluid-tight contact With the central 7 side wall and the flexible side walls 27. This construction also accommodates for normal wear of the parts over extended periods of service. Since the side wall is flexible, it is able, under the influence of the force of the pressure ring, to adjust itself to minor dimensional changes occasioned by wear or other causes and thereby to maintain good side wall contact on either side resulting in long term satisfactory operation of the pump.

To further enhance the fluid-tight seal between theflexible side wall 27, the impeller 18 and impeller race ring 16, a small V groove 55 in the innerface of the pressure ring 28 of configuration commensurate with the diameter of the pump chamber 17, will relieve somewhat the pressure exerted by the resilient cushion 29 against the flexible side walls 27 in this region of the pumping chamber. Thus, there will be in this partially unsupported region somewhat less tendency than otherwise forthe flexible side walls to become distorted. The possibility of excessive wear of the parts in this region is thereby diminished.

Under operating conditions requiring low output pressure, the pressure ring 28 and helical springs 30 may be dispensed with as the natural or inherent bias of the flexible side wall against the impeller and impeller race ring will alone provide the necessary bias for proper sealing.

Sealing of the flexible side wall 27 with the input shaft 36 is achieved by utilization of an outwardly directed circumferential flange 56 disposed in the center of the flexible side wall 27 of lesser diameter than the input shaft 36. As the flexible side wall 27 is constructed of material such as Teflon which has an inherent elastic quality, the circumferential flange 56 will exert a continuing contracting force around the input shaft 36. By this means, a very satisfactory leak-proof, low friction seal between the side wall and the input shaft is attained.

, The ability of Teflon to deform slightly under moderate pressures is further taken advantage of to produce additional sealing between the impeller 18 and impeller race ring 16 as well as between the impeller 18 and its associated central side wall 15 and flexible side wall 27. First, an override allowance in the eccentricity of the eccentric cam 19 is provided and will insure a fluid-tight seal at the point of contact between the impeller race ring 16 and the impeller 18. Any excess override will be absorbed by the elasticity of the Teflon material. Secondly, the impeller 18 may be dimensioned slightly thicker than its associated impeller race ring 16 whereby the elastic properties of the Teflon in absorbing this overdimension will further insure a fluid-tight seal between the impeller 18 and its associated central side wall 15 and flexible side wall 27. Additionally, the impeller vane 26 may be similarly over-dimensioned with respect to the impeller race ring 16 to accordingly insure a fluid-tight seal.

The bearings 39 disposed in the end bells 31, as best seen in FIG. 3, may additionally be of a fluorocarbon plastic material to further insure that any leakage of the fluid being pumped from the flexible side wall through the outwardly directed circumferential flange 56 will not cause corrosive damage to the bearings for the input shaft 36.

The flexible side wall 27 can also be suitably biased against the impeller 18 and impeller race ring 16 by means of a gas pressure applied to the outer cavity of the end bells 31. In this arrangement, the pressure ring 28 and associated helical springs 60 would notbe required. A pressurized assembly of this kind would afford absolute protection against outward fluid leakage from the circumferential flange seal.

In operation of the pump, depending upon the direction of rotation of theimpellers 18, the fluid to be pumped will be drawn through one of the ports 57 and carried around the circumference of the pumping chamber 17 in front of the point of contact of the impeller 18 with the pumping chamber 17 and accordingly discharged out the other of the ports 57, such eccentric or rotary type of 6 pumping action itself being well known to those skilled in the art.

If the eccentric cams 19 are disposed out of phase with each other, then the impellers will likewise be orbiting within the pumping chambers 180 out of phase and the discharge from the pump will be continuous since the pumping action is sinusodial in nature and the sum of the two sinusoidal discharges 180 out of phase will be constant.

The rotary pump according to the present invention is capable of continuous and constant flow rates from near Zero to those in the high milliliter range. Further, the discharge or flow rate of the pump of the present invention is linear in relation to the input shaft speed due to its low internal and external leakage resulting from the pumps unique construction. This linear relationship continues from maximum shaft input speed down to zero speed at which time the rotary pump acts as a closed valve interposed between the inlet and outlet fluid lines.

A useful aspect of the linear relationship between the shaft rotation and the fluid flow is the fact that the total volume of fluid being pumped between a starting and stopping point will be directly proportional to the total angular displacement of the shaft.

It is anticipated that a single pump unit according to the present invention may be used or two or more pump units may be stacked in tandem to operate from a common shaft power supply.

Having thus described the invention, it will be appreciated that other modifications thereof may be suggested to those of ordinary skill in the art within the scope and spirit of the appended claims.

What is claimed is:

1. In positive displacement rotary pumps of the type including a pump body member, an impeller member supported for orbital pumping action within the pump body member and an impeller vane disposed between the pump body member and impeller member and secured to one member and movable in a vane guide in the other member during pumping action of said impeller member, the improvement in said vane guide comprising:

a vane guide having two oppositely disposed side walls formed integral with one member, at least one of which is 'a flexible and resilient side wall spaced from the other a distance less than the thickness of said impeller vane whereby upon pumping action of said impeller, the flexible and resilient action of the side wall of the vane guide will provide a fluid-tight seal between the vane guide and the impeller vane.

2. The vane guide of claim 1 further including spring means for biasing at least one of said side walls of said vane guide toward said impeller vane.

3. A positive displacement rotary pump comprising:

a pump body;

an impeller disposed within said pump body and supported for orbital pumping action therein;

an impeller vane disposed between said pump body and said impeller and having one end thereof secured to said impeller; and

an impeller vane guide having two oppositely disposed side walls formed integral with said pump body, at least one of which is a flexible and resilient side wall for engagement with said impeller vane whereby upon orbital pumping action of said impeller, the flexible and resilient side wall of the vane guide will provide a fluid-tight seal between the impeller vane and the pump body as the impeller vane is reciprocating within the impeller vane guide.

4. The rotary pump of claim 3 wherein said impeller vane guide includes a relief cavity in said pump body adjacent at least one side of said impeller vane guide to further enhance the flexibility of said vane guide.

5. The rotary pump of claim 3 wherein said side walls of said impeller vane guide are spaced one from another a distance less than the thickness of said impeller vane whereby the flexible resilient side wall will adjust accordingly to the impeller vane, thereby eflecting a positive sealing engagement between the side walls of the vane guide and the impeller vane.

6. The rotary pump of claim 3 wherein said impeller vane guide is a fluorocarbon plastic.

7. The rotary pump of claim 3 further including springbias means for urging the flexible and resilient side wall of said impeller vane guide toward said impeller vane to enhance the sealing relation between the impeller vane and impeller vane guide.

8. The rotary pump of claim 7 including a cavity disposed adjacent said impeller vane guide and within said pump body and wherein said spring-bias means is disposed within said cavity whereby said spring means is isolated from contact with the fluid being pumped.

9. The rotary pump of claim 7 wherein said springbiasing means is formed of a noncorrosive material.

10. The rotary pump of claim 7 wherein said springbiasing means has an outer covering comprising a noncorrosive material.

'11. A positive displacement rotary pump comprising:

a pump body formed of a resilient and chemically inert material having a substantially circular pump chamber therein and an impeller vane guide extending from said pump chamber inwardly of said pump body;

a substantially dumbbell-shaped cavity within said main pump body at the termination of said impeller vane guide to provide relieved sections adjacent the walls of said impeller vane guide;

an impeller of chemically inert material disposed within said pump body and supported for orbital pumping action therein; and

an impeller vane of chemically inert material having one end thereof secured to said impeller and the opposite end thereof disposed in said impeller vane guide.

12. The rotary pump of claim 11 further including spring-bias means disposed within said cavity for urging said walls of the impeller vane guide inwardly toward one another to maintain a constant pressure against said impeller vane.

13. A positive displacement rotary pump comprising:

an impeller race member having a pump chamber therein;

an impeller disposed within said race member and supported for orbital pumping action therein; and

side wall members disposed on adjacent sides of said race member, at least one of which is a flexible side wall whereby the flexibility of said flexible side wall will adjust for normal wear and dimensional discrepancies between said impeller race member and said impeller for maintaining a continuous fluidtight seal.

14. The rotary pump of claim 13 wherein said side wall members, said impeller race member and said impeller are composed of fluorocarbon plastic material to thereby provide a rotary pump of low internal friction and high resistance to corrosion.

15. The rotary pump of claim 14 wherein said impeller is of slightly greater thickness than its associated impeller race ring to provide a fluid-tight seal between the impeller and side wall members.

16. The rotary pump of claim 14 wherein said impeller is supported for orbital pumping action within said pumping chamber so as to have an override therein within the elastic limits of the fluorocarbon plastic material to provide a positive fluid seal between the impeller and impeller race member.

17. The positive displacement rotary pump of claim 13 further including means for biasing said flexible side wall into engagement with said impeller race member and said impeller to enhance the fluid-tight seal therebetween.

18. The positive displacement rotary pump of claim 17 wherein said means for biasing said flexible side wall includes a pressure ring in engagement with said flexible side wall.

19. The rotary pump of claim 18 further including a resilient member disposed between said pressure ring and said flexible side wall for insuring the desired distribution of pressure between the pressure ring and the flexible side wall.

20. The rotary pump of claim 18 wherein said pressure ring includes a relieved section in the face thereof in engagement with said flexible side Wall of configuration commensurate with the pump chamber of said impeller race member to thereby relieve undue pressures at the side of the pump chamber resulting from engagement of the impeller with said pump chamber.

21. A positive displacement rotary pump comprising:

at least one relatively rigid side wall member;

a pump unit including a race ring and an impeller disposed adjacent at least one side of said rigid side wall member;

a flexible side wall member disposed adjacent said pump unit which together with said relatively rigid side wall defines a pumping chamber; and

means for maintaining said flexible side wall member, said pump unit and said rigid side wall member in engagement one with another thus to provide a fluidtight rotary pump capable of adjustment for wear and dimensional discrepancies.

22. A positive displacement rotary pump comprising:

a central side wall member having intake and discharge ports therein;

an impeller race ring disposed adjacent each side of said central side wall member and each having a substantially circular opening therein;

an input shaft disposed through said central side wall member and said impeller race rings and positioned concentric within said circular opening in each of said impeller race rings;

an impeller for each impeller race ring eccentrically journaled on said input shaft within said circular opening for orbital oscillation therein;

a flexible side wall disposed ajacent each of said impeller race rings and in engagement therewith to thereby define a pump chamber for each impeller; and

biasing means for urging said flexible side walls inwardly toward each other whereby said flexible side wall members, impeller race rings, impellers and central side wall member are maintained in fluidtight relationship one to another while providing for wear and dimensional discrepancies therebetween.

23. The rotary pump of claim 22 wherein said input shaft is encased in a chemically inert material and said flexible side walls include outwardly directed circumferential flanges thereon is sealing engagement with the encasement of said input shaft thereby providing a fluidtight and noncorrosive seal therebetween.

24. The rotary pump of claim 22 where said central side wall, said flexible side wall members, said impeller race rings and said impellers are composed of fluorocarbon plastic material;

said impeller is of slightly greater thickness than said associated impeller race ring; and

said impeller is journaled on said shaft with a slight excess of eccentricity so as to provide an override against the circular opening of said impeller race member whereby, due to the inherent properties of fluorocarbon plastic, a rotary pump will be provided of extremely low internal and external leakage as well as of low internal friction and high chemical resistively.

(References on following page) References Cited UNITED STATES PATENTS Stiven 103-132 Keith 103-123 Handley 103-132 Boyer 230-147 BOgre 10.3-132 Rolaif 230-145 Fraser 103-132 Gordinier 103-132 10 3,139,036 6/1964 McGill 230-145 3,166,017 1/1965 Mamo 103-130 FOREIGN PATENTS 5 7,126 1913 Great Britain. 29,928 1910 Great Britain. 273,536 7/ 1927 Great Britain. 296,482 9/ 1928 Great Britain. 315,363 2/1930 Great Britain.

10 DONLEY J. STOCKING, Primary Examiner.

W. J. GOODLIN, Assistant Examiner. 

1. IN POSITIVE DISPLACEMENT ROTARY PUMPS OF THE TYPE INCLUDING A PUMP BODY MEMBER, AN IMPELLER MEMBER SUPPORTED FOR ORBITAL PUMPING ACTION WITHIN THE PUMP BODY MEMBER AND AN IMPELLER VANE DISPOSED BETWEEN THE PUMP BODY MEMBER AND IMPELLER MEMBER AND SECURED TO ONE MEMBER AND MOVABLE IN A VANE GUIDE IN THE OTHER MEMBER DURING PUMPING ACTION OF SAID IMPELLER MEMBER, THE IMPROVEMENT IN SAID VANE GUIDE COMPRISING: A VANE GUIDE HAVING TWO OPPOSITELY DISPOSED SIDE WALLS FORMED INTEGRAL WITH ONE MEMBER, AT LEAST ONE OF WHICH IS A FLEXIBLE AND RESILIENT SIDE WALL SPACED FROM THE OTHER A DISTANCE LESS THAN THE THICKNESS OF SAID IMPELLER VANE WHEREBY UPON PUMPING ACTION OF SAID IMPELLER, THE FLEXIBLE AND RESILIENT ACTION OF THE SIDE WALL OF THE VANE GUIDE WILL PROVIDE A FLUID-TIGHT SEAL BETWEEN THE VANE GUIDE AND THE IMPELLER VANE. 